1. Field of the Invention
The present invention relates to methods for filling defined embroidery patterns with satin-like embroidery stitches, and more particularly to such methods in which a predefined interstitch spacing between adjacent turning stitches, which may be a constant, is maintained as the pattern is filled regardless of any variation in curvature of the pattern shape.
2. Description of the Related Art
The satin stitch and its many variations, such as tatami stitches, is a well known technique in embroidery for filling shapes, such as shown by way of example in U.S. Pat. No. 5,592,891 or the commonly owned copending U.S. paten application Ser. No. 08/794,010, filed Feb. 3, 1997, U.S. Pat. No. 5,809,921 and entitled xe2x80x9cMethod For Generating a Continuously Stitched Regional Carved Fill Composite Embroidery Stitch Patternxe2x80x9d. This class of stitch is generally characterized by lines of stitching which run in alternate directions and can be used to fill defined embroidery pattern shapes, such as illustrated in FIGS. 1 and 2, respectively, with parallel lines of stitching (FIG. 1) or lines of stitching which turn to follow the defined shape (FIG. 2). In filling such patterns, there is a desire to try to maintain a predefined stitch density and interstitch spacing, which may be a constant, throughout the entire filled pattern; however, prior art attempts at doing this where the pattern to be filled has a curved shape have not been satisfactory, particularly where there are numerous variations in curvature of the pattern shape.
Stitch density is normally determined by the distance between adjacent stitches or by the number of stitches per inch. In either case, a determination must be made as to where this distance is to be determined, such as at the end points of the stitch or at some distance in from the end point of the stitch. When the pattern shape to be filled is rectilinear or parallel stitches are being employed to fill the pattern shape, there is no real difference. However, this is not so when the stitches turn to follow a curving pattern shape, such as illustrated in FIG. 2. When the stitches turn, determining this distance at the end points of the stitch produces more stitches then if it is determined at a set distance in from the end points of the stitch. In the prior art, this determination has varied depending on the desired results and some have determined the density at the end points of the stitch while others have fixed it at a point 25% or 33% in from the end point of the stitch. The advantage to setting this determination at the end points of the stitch is that the stitch density is more consistent in wide turning satin stitch or tatami stitch columns, while the disadvantage is that more short stitching is required in order to maintain even stitch coverage in the inside of the turn. The problems in the prior art in producing a satisfactory filled pattern were magnified by unsatisfactory prior art attempts to generate stitches at a predefined, such as a constant, desired interstitch spacing or distance throughout the pattern as the pattern and the stitches turn. Three examples of such unsatisfactory prior art solutions to this problem are illustrated in FIGS. 3 through 8. FIGS. 3 and 4 illustrate an unsatisfactory prior art approach in which the outside end points of the stitches are placed at a specified interstitch distance, or isd, apart. As illustrated in FIGS. 3 and 4, this approach results in placing insufficient space between the stitches when the pattern shape being filled is locally sloped relative to the stitches. FIGS. 5 and 6 illustrate another unsatisfactory prior art approach in which a point r is first constructed that is a specified distance away from the outside end point of the previous stitch along a vector that is perpendicular to the previous stitch, and then the actual stitch that passes through this point, but lies inside the shape being filled, is then created. As illustrated in FIGS. 5 and 6, this prior art approach places insufficient spacing between turning stitches when the stitches are turning to follow the curving pattern shape, with this problem worsening the more tightly the stitches turn. Finally, FIGS. 7 and 8 illustrate still another unsatisfactory prior art approach, which is really an enhancement to the unsatisfactory method described with respect to FIGS. 5 and 6. In this prior art approach, an inset percentage is specified which controls the starting point for the creation of the point r employed in the prior method. The basic intent is that this point r be as close to the edge of the pattern shape as possible. This prior art method assumes that the user will specify an appropriate inset, with the appropriate value of the inset being determined by the amount of curvature of the pattern shape. This prior art method, like the other prior art methods discussed above, assumes that a single fixed inset is appropriate for the entire pattern shape. However, pattern shapes may normally exhibit a wide range of curvature and, accordingly, this method results in some spots having insufficient spacing and other spots having too much spacing between stitches as the curvature of the pattern varies, such as illustrated in FIGS. 7 and 8. These disadvantages of the prior art are overcome by the present invention which provides for a constant interstitch spacing regardless of variations in the curvature of the pattern shape being filled.
A method of filling a defined embroidery pattern shape comprising a curve defining the shape, which is filled with a plurality of turning satin-like embroidery stitches which turn to follow the defined shape, maintains a predefined interstitch spacing, such as a constant, between adjacent turning satin-like embroidery stitches as the defined shape is filled with the satin-like embroidery stitches. In carrying out the method, the density inset for the next adjacent satin-like embroidery stitch is dynamically varied in accordance with any change in the defined shape from the previous stitch, taking into account the stitch length and stitch angle. The associated end points of the next stitch are brought within an appropriate density inset distance from the previous adjacent stitch for maintaining the predefined interstitch spacing by creating an initial stitch having an associated end point along the curve defining the pattern shape and then creating a next stitch having an associated end point along the curve which is a perpendicular distance from the previous stitch end point such that this distance is a predefined value, such as a constant, along the curve for each stitch in the plurality of stitches filling the pattern shape regardless of any variation in curvature of the curve defining the pattern shape while the density inset for a given stitch dynamically varies as needed. The process is iteratively repeated, using the constant perpendicular distance from the previous stitch end point to the new stitch end point, until the defined pattern shape is completely filled with the satin-like embroidery stitches. Such satin-like embroidery stitches include both satin stitches and tatami stitches, with a tatami stitch being a variation of a satin stitch.